In widgets:

• windowHandle() only works for top level widgets (windows), so we need to first get the actual window() as windowHandle() is always nullptr for controls like ComboBox

In QtQuick Controls:

• we would just blow up for accessing widget which is null here. Use the QQuickWindow of the QQuickItem, if any. Given how long this went unnoticed shows that Qt *never* ever had icons working in ComboBoxes in QtQuick...

5.15

No longer blows up when I try to use icons in QQC2 desktop style ComboBox
Didn't notice any visual difference in widget combobox rendering despite it now supposedly doing something wrt scaling?

Compiled with and without BREEZE_HAVE_QTQUICK